Tin dioxide (SnO2) is widely used as an electron transport layer (ETL) in efficient and stable perovskite solar cells (PSCs) due to its excellent optoelectronic properties and low-temperature solution preparation process. However, SnO2 ETLs fabricated by the conventional solution method have many defects, among which Sn dangling bonds (i.e., oxygen vacancies) are particularly prominent. Herein, a simple buried interface engineering is employed to introduce phenyl-phosphinic acid (PPA) into the surface of SnO2 film for the preparation of highly efficient PSCs. A series of test results have shown that the phosphate group (PO) in PPA can not only passivate oxygen vacancy defects on the surface of SnO2, but also improve the film-forming quality of the upper perovskite, thereby exhibiting better photoelectric conversion efficiency (PCE) and stability. Ultimately, the optimized device achieves a maximum PCE of 22.81 %, an improvement of about 15 % over the control device (19.82 %). Meanwhile, the nonencapsulated device based on SnO2-PPA ETL shows much better storage and light stability than the control SnO2.
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